The present invention relates generally to distance and position determination systems, and more specifically to a system and method for accurately estimating the position of a locomoting individual relative to a fixed benchmark or starting point.
Position (or location) determination has become much more accurate in recent times. In years past, travelers developed various navigation techniques that involved determination of position according to landmarks and the individual""s position in relation to them. The success of this system, of course, depended on the availability of recognizable landmarks and the observer""s familiarity with them, either through an adequate description presented orally or in a written document. The landmarks could be natural or constructed, fixed or temporary, these factors varying according to the level of reliability required and the availability and cost of landmarks more reliable.
The sun and moon served as landmarks of sorts, although some knowledge of their (apparent) movement was necessary for accurate reckoning. When visible, the stars of the night sky provided an even more valuable landmark, although to make proper use of them required instruments for accurately gauging their position and charts applicable to varying locations and times of year were generally required. Despite these limitations, the stars provided a relatively reliable means of navigation where no (other) recognizable landmarks were available, for example at sea.
Compasses provided a great aid to position determination as well when reliable maps became available. Although almost unfailing accurate in determining direction, absent magnetic disturbances, a compass does little to aid in the determination of position absent one of two methods. The first of these methods involves, again, recognizable landmarks. Using a reasonably accurate map, position can be determined by reading the direction to a plurality of visible and mapped landmarks, finding one""s position at or near the intersection of the various directional lines. For example, if a city shown on the map lies due East, and a mapped mounted peak due North, the individual""s mapped position is at the intersection of lines drawn from the city extending west and from the mountain extending south. Additional landmarks help confirm the location and determine it more accurately. Depending on the quality of the map, compass, and landmarks, this method could be extremely accurate. Absent any of these factors, of course, the method could be extremely inaccurate.
The second method of compass reckoning is for the individual to proceed from a known reference point in a certain direction as determined by following the compass. If this course is followed diligently and accurately, then the individual will know their position lies along the line radiating from the reference point in the pre-established direction. This may be sufficient in itself, but often it will be desirable to determine a position point on this radiating line itself. For this, the rate of travel must be accurately measured in some way. Several methods are available. The individual could simply count paces and multiply by the length of one (presumably average) pace. If the individual is not walking, another method could be used, such as estimating a rate of travel and measuring the time in transit. Obviously, the journey could be subdivided to account for different pace lengths or rates of travel, to the extent that they can be determined. The distance could be directly measured, of course, for example by using a marked tape or wheel, although this may prove inconvenient over long distances. And any of these methods are compounded by changes in grade or obstacles, which may force the pace length or rate of travel to change, or make it difficult to use distance-measuring devices accurately. The same obstacles also make it difficult to stay true to the predetermined course and, therefore, further compounds the reckoning process even when reasonably accurate distance measurement is possible.
Despite their shortcomings, the various methods described above were widely used for many years, and not without some refinement. The advent of the Global Positioning System (GPS), however, advanced the art of position determination by a considerable degree. GPS uses signals sent from a plurality of satellites to allow an Earth-based instrument to determine its own location. Using such an instrument, an individual may determine their position almost anywhere on the Earth to an accuracy of several meters. And although a properly-calibrated instrument is required, the individual need possess no accurate knowledge of their own starting point or how far they have traveled from it.
A GPS, however, used for the navigation of ships and planes or for locating hikers lost in a wilderness area, cannot provide the precision of location necessary for successful information in some areas. In particular, where determination of a location within a building is concerned, the level of precision available is not sufficient. Yet position determination may be desirable for the provision, for example, of location-based services (LBS). LBS involves not finding an airport or a lost person, but rather the presentation of information, for example to a store patron, that is pertinent to the exact merchandise display next to them. Or, if a blind person is attempting to navigate through an office building or city market, the approximate location is already known. Far more precise location information is needed. In such a situation, of course, the fact that quite accurate location could be determined from landmarks is of little consequence.
There remains a need for a position location system that can both achieve a high degree of precision and be used by a person who is neither highly trained in using sophisticated instrumentation or predisposed to pay attention to the degree required to use them correctly.
In one aspect, the present invention is a system including a first short-range radio step sensor placed proximate to one foot of a pedestrian, and a second short-range radio step sensor placed proximate the other. Each sensor can detect when footfall has occurred, indicating another step has been taken, and initiating the collection of progress information. The system further included a processor coupled to a memory data-storage device for receiving and storing the progress information, both as received and in cumulative form. The system may further include an electronic compass for determining sensor orientation. Where an electronic compass is used in this manner, a learning program may be employed so that more accurate use of the progress information may be made based on the pedestrian""s walking-style habits as observed on a test path.
In another aspect, the present invention is a method of progress determination including the steps of providing a first and second radio step sensor, one placed proximate to each foot of the pedestrian. The system is initialized, and when a footfall is detected, progress information is collected and stored. The stored information is used to arrive at a cumulative position change with reference to the starting point. The progress information may include either the distance traveled or the direction of travel, or both. Where positional information is used, the method may further include the step of comparing the pedestrian""s cumulative progress to a stored map, and providing instructions for future travel.